Was your chicken fed caffeine, arsenic, Prozac or banned antibiotics?

New studies suggest that farmers may be feeding their chickens a long list of unusual substances.

What's in that chicken you're about to eat? Two new studies conducted by scientists at Johns Hopkins' Bloomberg School of Public Health and at Arizona State University found that chickens and turkeys from factory farms may be dosed up with caffeine, Benadryl, arsenic and several antibiotics that have been banned from use in poultry since 2005.

The levels of these substances aren't "an immediate health concern," co-author Keeve E. Nachman of Johns Hopkins told the New York Times. "But it makes me question how comfortable we are feeding a number of these things to animals that we're eating." He said that he and his fellow scientists were "floored" by what they found.

The studies, published in the journals Environmental Science & Technology and Science of the Total Environment, didn't study chicken meat but instead examined feather meal, which is a byproduct of poultry processing. According to the first paper's abstract, "feathers are converted by rendering into feather meal and sold as fertilizer and animal feed, thereby providing a potential pathway for reentry of drugs into the human food supply." The researchers studied the feather product because antimicrobials have the "the potential to bioaccumulate in poultry feathers."

The first study found that the feather meal samples they tested routinely contained the banned antibiotics known as fluoroquinolones, such as the drug Cipro. According to the Times, fluoroquinolones were banned from use in poultry because they can breed antibiotic-resistant "superbugs."

"The discovery of certain antibiotics in feather meal strongly suggests the continued use of these drugs, despite the ban put in place in 2005 by the FDA," the study's lead author, Bloomberg School microbiologist David Love, said in a prepared statement. "The public health community has long been frustrated with the unwillingness of FDA to effectively address what antibiotics are fed to food animals."

The study also found that most samples contained caffeine and one third of the samples contained the active antihistamine ingredient that is found in Benadryl. Many samples also contained acetaminophen, the active painkilling ingredient in Tylenol. As if that weren't enough, the samples tested that originated in China also contained the same active ingredient as the antidepressant Prozac.

The second study found that almost every sample studied contained Roxarsone, an organo-arsenic compound.

So why are farmers using these drugs? The caffeine keeps chickens awake so they eat more. The Benadryl, acetaminophen and Prozac reduce their anxiety, which can speed up their growth and improve the taste of their meat. The arsenic is used to give poultry meat a pleasant pink color. It also reduces infections in chickens.

The researchers say that the use of all of these chemicals could explain why drug-resistant superbugs are still at high levels in commercial poultry more than half a decade after the ban was put in place. They also say the arsenic "may pose additional risks to humans as a result of its use as an organic fertilizer and when animal waste is managed."

Nachman said the additives are probably not enough to directly affect the health of humans who consume the poultry, but he is cautious. "I've been studying food-animal production for some time, and the more I study, the more I'm drawn to organic," he told the Times.

Love and Nachman previously collaborated on a study that revealed drug residues in seafood. That study was published last year.